Along with recent popularization of compact labs, exposure of printing of silver halide photographic print paper is conducted at various kinds of places, and accordingly exposure is done under various conditions.
The use of exposure printers is accompanied by emission, which affects the temperature or humidity of ambient surroundings. Particularly, the use of color print paper, of which photographic performance is easily varied with temperature or humidity of the surroundings, causes unfavorable variation in color tone. Specifically at the time of starting of printing, print paper is easily affected under changes in temperature or humidity over time, producing problems such that in cases when a large number of prints of the same picture are made, a marked difference in tone between the start and the finish of printing occurs.
Iridium compounds are effective for improvement in reciprocity law failure, as disclosed in JP-B 43-4935 (hereinafter, the term, JP-B means a published Japanese Patent) and U.S. Pat. No. 4,997,751 and are also effective in increasing contrast. However, the use of the iridium compound results in deterioration in latent image stability at the initial stage after exposure, as described in Journal of Photographic Science vol. 33, page 201.
JP-A 10-307357 (hereinafter, the term, JP-A means an unexamined and published Japanese Patent Application) discloses a technique of introducing a deep and permanent electron trap into the interior of silver halide grains and satisfying a specified equation, thereby leading to enhanced high contrast of roomlight-handling photographic materials. JP-A 10-186558 discloses a technique of improving exposure dependence on humidity by the use of an emulsion evaluated on the basis of microwave photoconduction. However, sufficient photographic performance has not been obtained by these techniques.